One of conventionally available compressors is a rotary compressor including a cylinder which defines a cylinder chamber, a cylindrical-shaped roller which axially rotates while orbitally revolving within the cylinder chamber, a blade which is provided independent of the roller and which is held by the cylinder so as to be advanceable toward and withdrawable from within the cylinder chamber, and a drive shaft having an eccentric portion to be fitted to an inner circumferential sliding surface of the roller. In this rotary compressor, as the drive shaft is driven into rotation, the roller rotates and revolves within the cylinder chamber, and moreover moves relative to the blade. Further, the cylinder chamber is divided by the roller and the blade into a suction chamber and a compression chamber to perform suction and compression action.
With respect to this rotary compressor, in view of reducing mechanical loss by reducing the viscous shear loss of lubricating oil at the outer circumferential sliding surface of the eccentric portion and the inner circumferential sliding surface of the roller, a measure shown below has been proposed (JP 2541182 B). This measure is that the outer circumferential sliding surface of the eccentric portion of the drive shaft has a small-width portion provided on one side opposite to the load side, i.e. on a light-load side, of the outer circumferential sliding surface, to which less load is applied when the load is maximized, the small-width portion being made smaller than a large-width portion on the heavy-load side in terms of the axial width of the outer circumferential sliding surface, so that the viscous shear loss of oil at the outer circumferential sliding surface of the eccentric portion and the inner circumferential sliding surface of the roller is reduced to thereby reduce the mechanical loss.
The small-width portion of the outer circumferential sliding surface of the eccentric portion of the drive shaft is formed primarily by mechanical machining. In this case, while centers of the drive shaft body positioned on axial both sides of the eccentric portion are kept eccentric from the center of the rotating shaft of the machine, the machining work of the small-width portion needs to be carried out by accurately positioning the center of the eccentric portion at the center of the rotating shaft of the machine, hence being an extremely laborious machining work. Accordingly, it has been the case that the machining of the small-width portion would take quite large numbers of man-hours, resulting in higher costs of the conventional compressor.